1. Field of the Invention
This invention relates to image recording apparatus such as a printer and a copying machine, and more particularly to a novel image recording apparatus which is improved in recording speed, thus being effective in performing an image recording operation taking a relatively long time.
2. Description of the Related Art
One example of the conventional image recording apparatuses is a color copying machine which has been disclosed, for instance, by Japanese Patent Application Publication No. 20579/1980.
In the copying machine, a plurality of different developing units having different color developing agents are arranged around its photo-sensitive drum. As the photo-sensitive drum rotates, the latent images on the photo-sensitive drum are developed successively with the respective developing agents, and the images thus developed are transferred on a transfer roller in an overlap mode to form a full-color image, which is transferred onto the recording sheet.
With the image recording apparatus of this type, in order to obtain one color copy, it is necessary to rotate the photosensitive drum several turns. Hence, the apparatus suffers from the difficulty that its copying speed is much lower than that in the ordinary black and white copying operation.
In order to overcome this difficulty, it is necessary to increase the speed (process speed) of the photo-sensitive drum; however, an increase of the process speed is limited to the image forming process.
Under this condition, the color copying capability may be improved, for instance, by the following method: A plurality of color copying machines are operated simultaneously to print a plurality of recording sheets using one and the same original. In this case, the color copying capability can be increased as much as the number of copying machines.
However, the method is disadvantageous in the following points: Since it is necessary to install a plurality of color copying machines, the installation space is increased as much. Furthermore, since the color copying machines have their own sheet supply trays, it is necessary to perform the following troublesome operations: It is necessary to detect whether or not recording sheets are in the sheet supply trays of the color copying machines, to detect the number of recording sheets in each sheet supply tray, and to detect the kind of recording sheets (whether the recording sheets are ordinary ones or whether they are OHP sheets, for instance). In the case of using recording sheets having page numbers, the groups of recording sheets having predetermined page numbers must be set in the respective sheet supply trays of the color copying machines. Thus, it is essential to manage the recording sheets individually and separately.
In the apparatus, the recording sheets are supplied from the different sheet supply trays, and therefore the amount of positional shift (lateral shift in registration) of the recording sheet from the image on the photo-sensitive drum depends on the color copying machine; that is, different color copying machines provide different amount of positional shift. Hence, in this case, the images printed by the copying machines are greatly different in position. Thus, in this case, the positions of the sheet supply trays must be adjusted all over again.
The above-described technical difficulties are significant particularly in color image recording operations; however, it can be said that the same difficulties occur with the ordinary black and white image recording operations.